The capital murder trial of Tanner Horner resumed Monday without a jury in the courtroom, as the case entered a key legal step focused on vetting the defense’s expert witnesses.

Horner, a former FedEx contract driver, is accused of kidnapping and killing 7-year-old Athena Strand in Wise County in 2022. Prosecutors are seeking the death penalty.

On Monday, the court moved into what’s known as the voir dire phase for expert witnesses — a process where the judge and attorneys decide what testimony the jury will ultimately be allowed to hear.

Defense experts say Horner had serious health issues

Four medical experts called by the defense testified Monday outside the presence of the jury. All four said they had evaluated Horner and believed he had significant underlying health and developmental issues long before Athena’s death.

The witnesses included:

• A psychologist
• Two physicians who focus on environmental toxins
• A pediatrician

Across their evaluations, the experts said Horner was diagnosed with autism, fetal alcohol spectrum disorder and severe childhood lead poisoning. One doctor testified that Horner’s lead levels as a child were 24 times higher than those of typical peer groups.

They also described evidence of serious head trauma earlier in his life.

The psychologist testified that Horner referred to an alter ego he called “Zero,” which she described as functioning more like an imaginary friend, a way for him to express thoughts and feelings he struggled to communicate directly.

Prosecutors challenge testing methods

Prosecutors pushed back on the defense experts’ conclusions, focusing not just on what they found but how they found it.

Those challenges will help the judge decide how much of the experts’ testimony, and which opinions, the jury will be allowed to hear when the trial resumes in full.

One of the most striking moments came from the psychologist’s testimony.

She said Horner admitted to killing Athena during her evaluation and offered a new explanation for why he kidnapped her. According to her testimony, Horner claimed he took Athena because he was “concerned she saw him using cocaine.”

But the psychologist also told the court that, in her professional opinion, Horner understands the difference between right and wrong — and that this is not an insanity case.

What is voir dire and why is this happening without the jury?

In most trials, “voir dire” is commonly associated with jury selection. But in capital cases like Horner’s, the term is also used for a separate, critical step: vetting expert witnesses and their methods before the jury hears them.

In this context, voir dire is: A pretrial or midtrial hearing held outside the presence of the jury and is used to test whether a witness is qualified and whether their methods are reliable and admissible

This process is standard. It is routine in capital cases and many serious felony cases for judges to hold these hearings to decide what expert opinions the jury will be allowed to hear.

The voir dire hearings are expected to continue on Tuesday, with four more witnesses scheduled to appear.

Full testimony in front of the jury is set to resume on Wednesday.

The judge also indicated that the defense’s first witness, once the jury is back in the courtroom, is expected to be Tanner Horner’s mother.